U.S. patent application number 17/362515 was filed with the patent office on 2021-12-30 for detection and extraction of plastic contaminants within water using hydrophobic deep eutectic solvents.
The applicant listed for this patent is University of Kentucky Research Foundation. Invention is credited to Jameson Hunter, Wenqi Li, Qing Shao, Jian Shi, Yuxuan Zhang.
Application Number | 20210403346 17/362515 |
Document ID | / |
Family ID | 1000005738190 |
Filed Date | 2021-12-30 |
United States Patent
Application |
20210403346 |
Kind Code |
A1 |
Shi; Jian ; et al. |
December 30, 2021 |
DETECTION AND EXTRACTION OF PLASTIC CONTAMINANTS WITHIN WATER USING
HYDROPHOBIC DEEP EUTECTIC SOLVENTS
Abstract
Methods for detecting and extracting plastic contaminants within
a water sample, which involve introducing the water sample to a
hydrophobic deep eutectic solvent, are provided.
Inventors: |
Shi; Jian; (Lexington,
KY) ; Li; Wenqi; (Lexington, KY) ; Hunter;
Jameson; (Lexington, KY) ; Zhang; Yuxuan;
(Lexington, KY) ; Shao; Qing; (Lexington,
KY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
University of Kentucky Research Foundation |
Lexington |
KY |
US |
|
|
Family ID: |
1000005738190 |
Appl. No.: |
17/362515 |
Filed: |
June 29, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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63046226 |
Jun 30, 2020 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 11/0492 20130101;
C02F 2101/34 20130101; C02F 1/26 20130101; G01N 21/94 20130101;
G01N 33/18 20130101 |
International
Class: |
C02F 1/26 20060101
C02F001/26; B01D 11/04 20060101 B01D011/04; G01N 33/18 20060101
G01N033/18; G01N 21/94 20060101 G01N021/94 |
Goverment Interests
GOVERNMENT INTEREST
[0002] This invention was made with government support under grant
number 1018315 awarded by the United States Department of
Agriculture (USDA). The government has certain rights in the
invention.
Claims
1. A method for detecting plastic contaminants within a water
sample, comprising: introducing the water sample to a hydrophobic
deep eutectic solvent; and examining the hydrophobic deep eutectic
solvent for plastic contaminant enrichment after a period of
interaction with the water sample.
2. The method according to claim 1, wherein introducing the water
sample to the hydrophobic deep eutectic solvent includes mixing the
water sample with the deep eutectic solvent to form a mixture, and
wherein the hydrophobic deep eutectic solvent is examined for
plastic contaminant enrichment following phase separation between
the hydrophobic deep eutectic solvent and an aqueous portion of the
mixture.
3. The method according to claim 1, wherein the hydrophobic deep
eutectic solvent includes a hydrogen bond acceptor and a hydrogen
bond donor mixed in a molar ratio of about 0.1 to about 10 of
hydrogen bond acceptor to about 1 of hydrogen bond donor.
4. The method according to claim 1, wherein the hydrophobic deep
eutectic solvent includes a hydrogen bond acceptor selected from
one of decanoic acid and thymol.
5. The method according to claim 1, wherein the hydrophobic deep
eutectic solvent includes a hydrogen bond donor selected from one
of lidocaine and menthol.
6. The method according to claim 1, wherein the hydrophobic deep
eutectic solvent includes decanoic acid and menthol.
7. The method according to claim 6, wherein the decanoic acid and
menthol are mixed in a molar ratio of about 1:1.
8. The method according to claim 6, wherein the decanoic acid and
menthol are mixed in a molar ratio of about 1:2.
9. The method according to claim 1, wherein the hydrophobic deep
eutectic solvent includes thymol and menthol.
10. The method according to claim 9, wherein the thymol and menthol
are mixed in a molar ratio of about 1:1.
11. The method according to claim 9, wherein the thymol and menthol
are mixed in a molar ratio of about 2:1.
12. The method according to claim 2, wherein the hydrophobic deep
eutectic solvent is mixed with the water sample in a volume to
volume ratio from about 1:10 to about 1:1.
13. The method according to claim 1, wherein the plastic
contaminants include at least one of nanoplastics and
microplastics.
14. The method according to claim 1, wherein the plastic
contaminants include polyethylene terephthalate.
15. The method according to claim 1, wherein the hydrophobic deep
eutectic solvent is examined for plastic contaminant enrichment via
at least one of microscopy, spectrophotometry, and
thermogravimetric analysis.
16. A method for extracting plastic contaminants within a water
sample, comprising: introducing the water sample to a hydrophobic
deep eutectic solvent for a period of interaction sufficient for
the hydrophobic deep eutectic solvent to extract at least some of
the plastic contaminants from the water sample.
17. The method according to claim 16, wherein the hydrophobic deep
eutectic solvent includes (i) a hydrogen bond acceptor selected
from one of decanoic acid and thymol and (ii) a hydrogen bond donor
selected from one of lidocaine and menthol.
18. The method according to claim 17, wherein introducing the water
sample to the hydrophobic deep eutectic solvent includes mixing the
water sample with the hydrophobic deep eutectic solvent for a
period of interaction sufficient to extract at least 60% of the
plastic contaminants from the water sample.
19. The method according to claim 17, wherein introducing the water
sample to the hydrophobic deep eutectic solvent includes mixing the
water sample with the hydrophobic deep eutectic solvent for a
period of interaction sufficient to extract at least 70% of the
plastic contaminants from the water sample.
20. The method according to claim 17, wherein introducing the water
sample to the hydrophobic deep eutectic solvent includes mixing the
water sample with the hydrophobic deep eutectic solvent for a
period of interaction sufficient to extract at least 80% of the
plastic contaminants from the water sample.
21. The method according to claim 17, wherein introducing the water
sample to the hydrophobic deep eutectic solvent includes mixing the
water sample with the hydrophobic deep eutectic solvent for a
period of interaction sufficient to extract at least 90% of the
plastic contaminants from the water sample.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 63/046,226, filed Jun. 30, 2020, the
entire disclosure of which is incorporated herein by this
reference.
TECHNICAL FIELD
[0003] The presently-disclosed subject matter generally relates to
the detection and extraction of contaminants within a water sample.
In particular, the presently-disclosed subject matter relates to
methods for detecting and extracting plastic contaminants within a
water sample, which involve introducing the water sample to a
hydrophobic deep eutectic solvent.
BACKGROUND
[0004] Long-time human activities have led to the widespread
deposit of plastic debris into the global aqueous system.
Accumulation of micro- and nano-scale plastic particles (i.e.,
"microplastics" and "nanoplastics," respectively) is the subject of
increasing concern as their small size make them hard to remediate
using traditional methods. Nanoplastics and microplastics refer to,
nanoscale and microscale plastic particles, respectively, composed
of organic polymers, such as polystyrene, polyethylene,
polypropylene, and polyethylene terephthalate (PET). Nanoplastics
and microplastics can be generated through various paths, such as
through the mechanical and chemical degradation of plastic wastes
widely used for personal and industrial activities. Prior research
has identified the presence of nanoplastics within various aqueous
systems, including seawater and drinking water. The small size of
nanoplastics could make them impact the ecosystem differently from
the micro- and macro-plastics. With sizes similar or even smaller
than a cell, nanoplastics can penetrate the natural barriers of
plants, animals, and humans and thus affect the biological
functions of the same. Although the interaction between
nanoplastics and ecosystems and the mode of action are still an
active area of research, recent studies have revealed that
nanoplastics can potentially change the metabolism of human lung
cells and significantly decrease the rate of fertilization success
of oysters. To date, however, the detection and quantification of
nanoplastics within contaminated water samples remains challenging
due to the difficulty in collecting nanoplastics from water.
[0005] Accordingly, there is a need for additional methods for
detecting and extracting plastic contaminants within water
samples.
SUMMARY
[0006] The presently-disclosed subject matter meets some or all of
the above-identified needs, as will become evident of those of
ordinary skill in the art after a study of information provided in
this document.
[0007] This Summary describes several embodiments of the
presently-disclosed subject matter, and in many cases lists
variations and permutations of these embodiments. This Summary is
merely exemplary of the numerous and varied embodiments. Mention of
one or more representative features of a given embodiment is
likewise exemplary. Such an embodiment can typically exist with or
without the feature(s) mentioned; likewise, those features can be
applied to other embodiments of the presently-disclosed subject
matter, whether listed in this Summary or not. To avoid excessive
repetition, this Summary does not list or suggest all possible
combinations of such features.
[0008] The presently-disclosed subject matter includes methods and
compositions for use in the detection and extraction of plastic
contaminants within a water sample.
[0009] In some embodiments of the presently-disclosed subject
matter, a method is provided for detecting plastic contaminants
within a water sample using a hydrophobic deep eutectic solvent
(DES), which involves introducing a water sample to the hydrophobic
DES; and examining the hydrophobic DES for plastic contaminant
enrichment (i.e., the presence of plastic contaminants within the
hydrophobic DES) after a period of interaction with the water
sample. In some embodiments of the method for detecting plastic
contaminants within the water sample, the water sample is
introduced to the hydrophobic DES by mixing the water sample with
the deep eutectic solvent to form a mixture, and then examining the
hydrophobic DES for plastic contaminant enrichment following phase
separation between the hydrophobic DES and an aqueous portion of
the mixture. In some embodiments, the hydrophobic DES is mixed with
the water sample in a volume to volume ratio from about 1:10 to
about 1:1. In some embodiments, the hydrophobic DES may be examined
for contaminant enrichment via at least one of microscopy,
spectrophotometry, and thermogravimetric analysis. In some
embodiments, the hydrophobic DES may be examined for plastic
contaminant enrichment by examining the optical density of the
aqueous portion of the mixture.
[0010] In some embodiments of the presently-disclosed subject
matter, a method for extracting plastic contaminants within a water
sample is provided, which involves introducing the water sample to
a hydrophobic DES for a period of time sufficient to extract at
least some of the plastic contaminants from the water sample. In
some embodiments, introducing the water sample to the hydrophobic
DES includes mixing the water sample with the hydrophobic DES for a
period sufficient to extract at least 60% of the plastic
contaminants from the water sample. In some embodiments,
introducing the water sample to the hydrophobic DES includes mixing
the water sample with the hydrophobic DES for a period sufficient
to extract at least 70% of the plastic contaminants from the water
sample. In some embodiments, introducing the water sample to the
hydrophobic DES includes mixing the water sample with the
hydrophobic DES for a period sufficient to extract at least 80% of
the plastic contaminants from the water sample.
[0011] In some embodiments, the water sample within the methods for
plastic contaminant detection and extraction provided herein is
freshwater. In some embodiments, the water sample is salty water.
In some embodiments the water sample is contaminated with at least
one of nanoplastics and microplastics. In some embodiments, the
water sample is contaminated with polyethylene terephthalate (PET).
In some embodiments, the water sample is contaminated with
polystyrene (PS). In some embodiments, the water sample is
contaminated with polypropylene (PP). In some embodiments, the
water sample is contaminated with polyethylene (PE). In some
embodiments, the water sample is contaminated with polylactic acid
(PLA). In some embodiments, the water sample is contaminated with
polybutylene succinate (PBS). In some embodiments, the water sample
is contaminated with polyhydroxyalkanoate (PHA). In some
embodiments, the water sample is contaminated with a mixture of PET
and/or PS and/or PP and/or PE and/or PLA and/or PBS and/or PHA
plastic particles.
[0012] Various hydrophobic DES compositions, each of which may be
utilized in the plastic contaminant detection and extraction
methods noted above, are also provided. In some embodiments, the
hydrophobic DES includes a hydrogen bond acceptor and a hydrogen
bond donor mixed in a molar ratio of about 0.1 to about 10 of
hydrogen bond acceptor (HBA) to about 1 of hydrogen bond donor
(HBD). In some embodiments, the HBA of the hydrophobic DES is
selected from one of decanoic acid and thymol. In some embodiments,
the HBD of the hydrophobic DES is selected from one of lidocaine
and menthol. In some embodiments the hydrophobic DES includes
decanoic acid and menthol mixed in a molar ratio of about 1:1 or
about 1:2. In some embodiments, the hydrophobic DES includes thymol
and menthol mixed in a molar ratio of about 1:1 or about 2:1.
[0013] Further features and advantages of the presently-disclosed
subject matter will become evident to those of ordinary skill in
the art after a study of the description, figures, and non-limiting
examples in this document.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The presently-disclosed subject matter will be better
understood, and features, aspects and advantages other than those
set forth above will become apparent when consideration is given to
the following detailed description thereof. Such detailed
description makes reference to the following drawings, wherein:
[0015] FIG. 1 is a table showing the formula for eight hydrophobic
DES compositions that may be used in the detection and extraction
of plastic contaminants within a water sample, with molar ratios of
the respective organic molecules of such compounds represented in
parentheses.
[0016] FIGS. 2A-2D show the chemical structures of the organic
molecules used in the synthesis of the hydrophobic DES compositions
of FIG. 1. (A) Chemical structure of decanoic acid (Dea). (B)
Chemical structure of thymol (Thy). (C) Chemical structure of
menthol (Men). (D) Chemical structure of lidocaine (Lid).
[0017] FIG. 3 is a scanning electron microscope (SEM) image of
synthetic polyethylene terephthalate (PET) nanoplastic particles, a
contamination commonly found in freshwater water bodies.
[0018] FIGS. 4A-4B are graphs showing the particle size
distribution of synthetic PET nanoplastic particles in (A) a
contaminated freshwater water sample and (B) a contaminated salty
water (3.5 wt % NaCl) water sample, as measured by dynamic laser
scattering (DLS).
[0019] FIGS. 5A-5D are images of an aqueous solution of freshwater
water sample contaminated with PET nanoplastic particles alone and
in combination with a hydrophobic DES comprising decanoic acid and
menthol at a 1:1 molar ratio (Dea:Men (1:1) DES). (A) Freshwater
water sample contaminated with PET nanoplastic particles alone. (B)
Contaminated freshwater water sample in combination with Dea:Men
(1:1) DES before mixing. (C) Mixture (1:1 v/v) of contaminated
freshwater water sample and Dea:Men (1:1) DES before phase
separation. (D) Mixture (1:1 v/v) of freshwater water sample and
Dea:Men (1:1) DES after phase separation.
[0020] FIGS. 6A-6B are images of a freshwater water sample
contaminated with PET nanoplastic particles in combination with a
hydrophobic DES comprising thymol and menthol at a 1:1 molar ratio
(Thy:Men (1:1) DES). (A) Mixture (1:1 v/v) of contaminated
freshwater water sample and Thy:Men (1:1) DES before phase
separation. (B) Mixture (1:1 v/v) of freshwater water sample and
Thy:Men (1:1) after phase separation.
[0021] FIG. 7 is an image of a mixture (10:1 v/v) of a freshwater
water sample contaminated with PET nanoplastic particles (bottom
layer) and Dea:Men (1:1) DES after phase separation (top
layer).
[0022] FIG. 8 is an image of a mixture (10:1 v/v) of a salty water
(3.5 wt % NaCl) water sample contaminated with PET nanoplastic
particles (bottom layer) and Dea:Men (1:1) DES after phase
separation (top layer).
[0023] FIG. 9 is an image showing the different contact angles
exhibited by freshwater, Dea:Men (1:1) DES, and Thy:Men (1:1) DES
on a PET film.
[0024] FIG. 10 is a snapshot of a metadynamic simulation system
with a PET 5-monomer chain (VDW mode) in a hydrophobic DES
comprising thymol and menthol in a 2:1 molar ratio (Thy:Men (2:1))
and freshwater interface.
[0025] FIG. 11 is a graph showing the free energy profile of the
PET 5-monomer chain around the Thy:Men (2:1) DES-freshwater
interface of FIG. 10.
[0026] FIG. 12 is a graph showing the percent of PET extracted from
a freshwater sample with a concentration of 1 mg/mL of plastic
contaminants over a period of 32 hours with constant stirring using
Dea:Men (1:1) DES; Dea: Men (1:2) DES; and Thy:Men (1:1) at 1:1 v/v
DES to water ratio.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0027] The details of one or more embodiments of the
presently-disclosed subject matter are set forth in this document.
Modifications to embodiments described in this document, and other
embodiments, will be evident to those of ordinary skill in the art
after a study of the information provided in this document. The
information provided in this document, and particularly the
specific details of the described exemplary embodiments, is
provided primarily for clearness of understanding and no
unnecessary limitations are to be understood therefrom. In case of
conflict, the specification of this document, including
definitions, will control.
[0028] The presently-disclosed subject matter includes a method for
detecting plastic contaminants within a water sample using a
hydrophobic deep eutectic solvent (DES). In the detection method,
the presence of plastic contaminants within a water sample is
detected by examining the hydrophobic DES for plastic contaminant
enrichment (i.e., the presence of plastic contaminants within the
hydrophobic DES) following a period of interaction with the water
sample. In this regard, the plastic contaminant detection method of
the present disclosure generally includes first introducing a
hydrophobic DES to a water sample, which may be contaminated with
plastic contaminants (e.g., microplastics and/or nanoplastics), and
then subsequently examining the hydrophobic DES for plastic
contaminant enrichment, with enrichment of the hydrophobic DES
indicating contamination of the water sample.
[0029] In some embodiments, following interaction with the water
sample, the hydrophobic DES may be examined for plastic contaminant
enrichment by way of visual examination. For example, in some
embodiments, the hydrophobic DES may be determined to be enriched
with plastic contaminants upon observing an increase in the
opaqueness of the hydrophobic DES following interaction with the
water sample. Additionally or alternatively, in some embodiments,
the hydrophobic DES may be examined for plastic contaminant
enrichment using microscopic, spectrophotometric, and/or
thermogravimetric (thermogravimetric analysis) methods. In some
embodiments, the hydrophobic DES may be examined using confocal
microscopy, Fourier-transform infrared spectroscopy, Raman
spectroscopy, and gas chromatography-mass spectrometry, or
combinations thereof. In some embodiments, examination of the
hydrophobic DES may include quantifying the number of plastic
contaminants within the enriched hydrophobic DES. In some
embodiments, the number of plastic contaminants within the enriched
hydrophobic DES may, in turn, be utilized to quantify the plastic
contaminants within the water sample. In some embodiments, the
hydrophobic DES may be examined for plastic contaminant enrichment
by examining the optical density of the aqueous portion of the
mixture.
[0030] In some embodiments, the hydrophobic DES is first introduced
to the water sample by mixing the hydrophobic DES with the water
sample to form a mixture, and then examined for plastic contaminant
enrichment following phase separation between the hydrophobic DES
and an aqueous portion of the mixture. In some embodiments, the
hydrophobic DES is mixed with the water sample at a hydrophobic DES
volume to water sample volume ratio ranging from about 1:1 v/v to
about 1:10 v/v. Mixing of the water sample and the hydrophobic DES
can be performed by way of vortex, agitation, decanting, crossflow,
or any other suitable means of mixing, as would be known to one of
skill in the art. In some embodiments, the mixture may be
centrifuged to further promote phase separation between the
hydrophobic DES composition and the aqueous portion of the
mixture.
[0031] As the DES is hydrophobic, it is nonpolar and thus
immiscible with the aqueous portion of the mixture. Thus, unlike
traditional deep eutectic solvents, which are water-miscible, the
hydrophobic DES does not have the potential to pollute the aqueous
system in which it is introduced. Rather, due to the aversion of
the hydrophobic DES to water and its affinity to nonpolar organic
compounds within the water sample, plastic contaminants within the
mixture are extracted from the aqueous portion and recovered in the
hydrophobic DES phase of the mixture following phase separation
(FIGS. 5D, 6B, 7, and 8), thus leaving an aqueous portion with
reduced plastic particle contamination. In this way, the
hydrophobic DES may thus be used to extract plastic contaminants
from, and thus reduce contamination of, a water sample.
[0032] Accordingly, in another aspect, the presently-disclosed
subject matter also includes a method for extracting plastic
contaminants from a water sample contaminated with plastic
contaminants. In some embodiments, the water sample and hydrophobic
DES are mixed for a period of interaction sufficient to extract at
least 10% of plastic contaminants from the water sample (FIG. 12).
In some embodiments, the water sample and hydrophobic DES are mixed
for a period of interaction sufficient to extract at least 20% of
plastic contaminants from the water sample (FIG. 12). In some
embodiments, the water sample and hydrophobic DES are mixed for a
period of interaction sufficient to extract at least 30% of plastic
contaminants from the water sample (FIG. 12). In some embodiments,
the water sample and hydrophobic DES are mixed for a period of
interaction sufficient to extract at least 40% of plastic
contaminants from the water sample (FIG. 12). In some embodiments,
the water sample and hydrophobic DES are mixed for a period of
interaction sufficient to extract at least 50% of plastic
contaminants from the water sample (FIG. 12). In some embodiments,
the water sample and hydrophobic DES are mixed for a period of
interaction sufficient to extract at least 60% of plastic
contaminants from the water sample (FIG. 12). In some embodiments,
the water sample and hydrophobic DES are mixed for a period of
interaction sufficient to extract at least 70% of plastic
contaminants from the water sample (FIG. 12). In some embodiments,
the water sample and hydrophobic DES are mixed for a period of
interaction sufficient to extract at least 80% of plastic
contaminants from the water sample (FIG. 12). In some embodiments,
the water sample and hydrophobic DES are mixed for a period of
interaction sufficient to extract at least 90% of plastic
contaminants from the water sample (FIG. 12).
[0033] Following phase separation of the hydrophobic DES and the
aqueous portion of the mixture, in some embodiments, the enriched
hydrophobic DES phase may be removed from the mixture for
subsequent examination.
[0034] As evidenced above, in some implementations, the methods of
the present disclosure include applying the hydrophobic DES
composition described herein directly in a two-phase system so that
plastic contaminants are extracted from an aqueous phase and
recovered in the hydrophobic DES phase. It should be appreciated,
however, that although interaction of the hydrophobic DES and the
water sample within the methods described herein is primarily
referred to as being facilitated by mixing the hydrophobic DES and
water sample together to form a mixture, alternative means of
hydrophobic DES and water sample interaction are also contemplated.
For example, in one alternative embodiment, the hydrophobic DES may
be immobilized on a support, such as a membrane or porous medium,
so that plastic contaminants in a water sample are extracted from
the water sample as the water sample passes through the support on
which the hydrophobic DES is disposed. In another alternative
embodiment, the plastic contaminant detection and extraction
methods may include cross-linking the hydrophobic DES to form a
polymeric hydrophobic DES structure and then mixing the polymeric
hydrophobic DES structure with a contaminated water sample
including plastic contaminants.
[0035] The hydrophobic DES utilized in the methods of the present
disclosure includes a hydrogen bond acceptor (HBA) and a hydrogen
bond donor (HBD).
[0036] In some embodiments, the hydrophobic DES includes a HBA
selected from one of: menthol (FIGS. 1 and 2C); thymol (FIGS. 1 and
2B); and decanoic acid (FIGS. 1 and 2A). Although the HBA of the
hydrophobic DES is primarily referred to herein as being menthol,
thymol, or decanoic acid, without wishing to be bound by theory, it
is contemplated that the HBA may alternatively be selected from one
of: methyltrioctylammonium bromide; methyltrioctylammonium
chloride; tetrabutylammonium bromide; tetrabutylammonium chloride;
tetraheptylammonium chloride; tetraoctylammonium chloride;
tetraoctylammonium bromide; dodecanoate sodium salt; and lauric
acid due to such HBAs low solubility in water. It is further
contemplated that, in some alternative embodiments the HBA may
comprise multiple HBAs.
[0037] In some embodiments, the hydrophobic DES includes a HBD
selected from one of: menthol (FIGS. 1 and 2C) and lidocaine (FIG.
1 and FIG. 2D). Although the HBD of the hydrophobic DES is
primarily referred to herein as being menthol or lidocaine, without
wishing to be bound by any particular theory, it is contemplated
that the HBD may alternatively be selected from one of: acetic
acid; acrylic acid; butyric acid; hexanoic acid; hexadecanol;
octanoic acid; oleic acid; decanoic acid; decyl alcohol; dodecyl
alcohol; lauric acid; lactic acid; levulinic acid; palmitic acid;
propionic acid; pyruvic acid; phenylacetic acid; myristic acid;
mandelic acid; nonanoic acid; cis-9-octadecenoic acid; ricinoleic
acid; ethylene glycol; 1-propanol; 1,3-propanediol; glycerol;
1-butanol; 1,2-butanediol; 1-tetradecanol; hexyl alcohol; capryl
alcohol; cyclohexanol; camphor; ibuprofen; ibuprofen acid;
perfluorodecanoic acid; stearic acid; and undecylenic acid. It is
further contemplated that, in some alternative embodiments the HBD
may comprise multiple HBDs.
[0038] In some embodiments, the hydrophobic DES is synthesized by
mixing the HBA and the HBD at a molar ratio ranging from about 0.1
to about 10 of HBA to about 1 of HBD. Following mixture of the HBA
and HBD, the eutectic mixture is preferably heated and constantly
stirred until a homogenous transparent liquid is obtained. In some
embodiments, heating of the eutectic mixture occurs at temperatures
of about 60.degree. C.
[0039] The HBA and HBD selected for use in the synthesis of the
hydrophobic DES and molar ratios corresponding to the same can be
selected and modified to extract specific substrates within a
contaminated water sample. In this regard a variety of different
hydrophobic DESs may be utilized in the methods of the present
disclosure. For example, in some embodiments, the hydrophobic DES
may comprise decanoic acid and menthol mixed at a molar ratio of
about 1:1 (FIG. 1) to extract PET-based plastic contaminants. In
another embodiment, the hydrophobic DES may comprise decanoic acid
and menthol mixed at a molar ratio of about 1:2 (FIG. 1). In
another embodiment, the hydrophobic DES may comprise decanoic acid
and lidocaine mixed at a molar ratio of about 2:1 (FIG. 1). In
another embodiment, the hydrophobic DES may comprise menthol and
lidocaine mixed at a molar ratio of about 2:1 (FIG. 1). In another
embodiment, the hydrophobic DES may comprise thymol and lidocaine
mixed at a molar ratio of about 2:1 (FIG. 1). In another
embodiment, the hydrophobic DES may comprise thymol and menthol
mixed at a molar ratio of about 1:1 (FIG. 1). In another
embodiment, the hydrophobic DES may comprise thymol and lidocaine
mixed at a molar ratio of about 1:1 (FIG. 1). In another
embodiment, the hydrophobic DES may comprise thymol and menthol
mixed at a molar ratio of about 1:2 (FIG. 1). Accordingly, in
another aspect, the presently-disclosed subject matter also
includes hydrophobic DES compositions, which may be utilized in the
plastic contaminant detection and extraction methods disclosed
herein.
[0040] As a result of the affinity of the hydrophobic DES to
certain organic compounds, the hydrophobic DESs and methods
disclosed herein may prove useful in the extraction of a variety of
plastic contaminants of different types and sizes. For example, in
some implementations, the water sample in the above-described
method may include nanoplastic and/or microplastic contaminants. In
some embodiments, the water sample in the above-described plastic
contaminant detection and extraction methods may include PET
plastic particles (FIG. 3). In some embodiments, the water sample
may include polystyrene (PS) plastic particles. In some
embodiments, the water sample may include polypropylene (PP)
plastic particles. In some embodiments, the water sample may
include polyethylene (PE) plastic particles. In some embodiments,
the water sample may include polylactic acid (PLA) plastic
particles. In some embodiments, the water sample may include
polybutylene succinate (PBS) plastic particles. In some
embodiments, the water sample may include polyhydroxyalkanoate
(PHA) plastic particles. In some embodiments, the water sample may
include a mixture of PET and/or PS and/or PP and/or PE and/or PLA
and/or PBS and/or PHA plastic particles.
[0041] Although discussed herein with respect to a "water sample,"
one of ordinary skill in the art will appreciate that application
and use of the compositions and methods described herein are not
bound to any particular volume of water. As such, the compositions
and methods described herein may prove useful in the extraction of
plastic contaminants from small volumes of contaminated water, such
as that contained within a personal drinking container, to large
volumes of contaminated water, such as lakes or rivers, alike.
[0042] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which the disclosure belongs. Any
methods and materials similar to or equivalent to those described
herein can be used in the practice or testing of the present
disclosure.
[0043] As used herein, and unless otherwise indicated, the term
"water sample" is understood to mean a sample which includes water
of any type which is or may become contaminated by plastic
contaminants, such as nanoplastics or microplastics. Accordingly,
unless indicated to the contrary, "water sample" encompasses
variations including: in some embodiments, the water sample
includes freshwater; in some embodiments, the water sample includes
brackish water; in some embodiments the water sample includes salty
water, such as seawater; and in some embodiments, the water sample
includes wastewater, such as from a municipal sewage or other
industrial system.
[0044] Following long-standing patent law convention, the terms
"a," "an," and "the" refer to "one or more" when used in this
application, including the claims. Thus, for example, reference to
"a cell" includes a plurality of cells, and so forth.
[0045] The terms "comprising," "including," "having," and
grammatical variations thereof are intended to be inclusive and
mean that there may be additional elements other than the listed
elements.
[0046] Unless otherwise indicated, all numbers expressing
quantities of ingredients, properties such as reaction conditions,
and so forth used in the specification and claims are to be
understood as being modified in all instances by the term "about."
Accordingly, unless indicated to the contrary, the numerical
parameters set forth in this specification and claims are
approximations that can vary depending upon the desired properties
sought to be obtained by the presently-disclosed subject
matter.
[0047] As used herein, the term "about," when referring to a value
or to an amount of mass, weight, time, volume, concentration,
percentage, or the like is meant to encompass variations of in some
embodiments .+-.50%, in some embodiments .+-.40%, in some
embodiments .+-.30%, in some embodiments .+-.20%, in some
embodiments .+-.10%, in some embodiments .+-.5%, in some
embodiments .+-.1%, in some embodiments .+-.0.5%, and in some
embodiments .+-.0.1% from the specified amount, as such variations
are appropriate to perform the disclosed method.
[0048] As used herein, ranges can be expressed as from "about" one
particular value, and/or to "about" another particular value. It is
also understood that there are a number of values disclosed herein,
and that each value is also herein disclosed as "about" that
particular value in addition to the value itself. For example, if
the value "10" is disclosed, then "about 10" is also disclosed. It
is also understood that each unit between two particular units are
also disclosed. For example, if 10 and 15 are disclosed, then 11,
12, 13, and 14 are also disclosed.
[0049] All combinations of method or process steps as used herein
can be performed in any order, unless otherwise specified or
clearly implied to the contrary by the context in which the
referenced combination is made.
[0050] As used herein, nomenclature for compounds, including
organic compounds, can be given using common names, IUPAC, IUBMB,
or CAS recommendations for nomenclature. When one or more
stereochemical features are present, Cahn-Ingold-Prelog rules for
stereochemistry can be employed to designate stereochemical
priority, ElZ specification, and the like. One of skill in the art
can readily ascertain the structure of a compound if given a name,
either by systemic reduction of the compound structure using naming
conventions, or by commercially available software, such as
CHEMDRAW.TM. (Cambridgesoft Corporation, U.S.A.).
[0051] As used herein, the terms "optional" or "optionally" means
that the subsequently described event or circumstance can or cannot
occur, and that the description includes instances where said event
or circumstance occurs and instances where it does not.
[0052] The presently-disclosed subject matter is further
illustrated by the following specific but non-limiting examples.
The following examples may include compilations of data that are
representative of data gathered at various times during the course
of development and experimentation related to the
presently-disclosed subject matter. Those skilled in the art will
recognize, or be able to ascertain, using no more than routine
experimentation, numerous equivalents to the specific substances
and procedures described herein.
EXAMPLES
[0053] The following examples focus on the discovery that certain
hydrophobic DESs, in addition to their aversion to water, also
exhibit an affinity towards plastic particles commonly found in
contaminated water. In light of the foregoing, the inventors of the
present disclosure have found that hydrophobic DESs synthesized
from the mixture of certain organic molecules can be utilized in
combination with contaminated water samples to effectively detect
and extract plastic contaminants. In particular, the following
examples show that that hydrophobic DESs synthesized from the
mixture of either decanoic acid and menthol or thymol and menthol
can be mixed with a contaminated water sample to detect and extract
nanoplastics therefrom. The examples further show that such
hydrophobic DESs do not pose a risk of further contaminating the
water sample in which they are introduced and exhibit a strong
affinity to PET-based plastics. Based on the foregoing, it is thus
believed the methods and hydrophobic DES compositions of the
present disclosure are effective tools which can be utilized in a
variety of environments and water purification applications in
which plastic contaminant detection or extraction is desired.
Example 1
[0054] Materials and Methods
[0055] Water Sample Preparation
[0056] Contaminated water samples including both freshwater and
salty water were prepared. PET pellets were first dissolved in
phenol with gentle mixing and heating at .about.60.degree. C. PET
phenol solution was then gradually added drop by drop into ethanol
at agitation of 600 RPM. By adjusting the agitation speed,
particles with different sizes can be generated. The nanoplastic
solution was centrifuged and resuspended in freshwater and salty
water (3.5 wt % NaCl to mimic seawater). As shown in FIG. 3, the
resulting nanoplastic particles resuspended in freshwater were
generally spherical with size distribution in a range of
.about.119.+-.22 nm as measured by dynamic laser scattering (DLS).
Some larger nanoplastic particles with a size of .about.194 nm
constituting potential outliers were also observed. Interestingly,
upon resuspending in salty water (3.5 wt. % NaCl), the nanoplastics
tended to aggregate into much large clusters with irregular shapes
of sizes in a range of 600-1000 nm. Zeta potential of PET
nanoparticles decreased from -41.4.+-.4.9 to 11.7.+-.3.1 in
freshwater and salty water, respectively, suggesting that PET
nanoparticles tend to aggregate at a high ionic salt solution.
[0057] Synthesis of Hydrophobic DESs
[0058] A first hydrophobic DES was synthesized by mixing decanoic
acid and menthol at a 1:1 molar ratio (Dea:Men (1:1) DES). A second
hydrophobic DES was synthesized by mixing thymol and menthol at a
1:1 molar ratio (Thy:Men (1:1) DES). Both the first and second
hydrophobic DESs appeared to be colorless, transparent liquids with
densities slightly less than the density of water. Each eutectic
mixture was followed by heating to 60.degree. C. with a constant
stirring until a homogenous and transparent liquid was
obtained.
[0059] Mixture of Water Sample and Hydrophobic DES
[0060] A total of four test samples were prepared for nanoplastic
extraction testing by combining the two hydrophobic DESs (i.e.,
Dea:Men (1:1) DES and Thy:Men (1:1) DES) with either contaminated
freshwater or contaminated salty water in different volume to
volume ratios (v/v). Specifically, a first sample was prepared by
combining Dea:Men (1:1) DES and contaminated freshwater at a 1:1
v/v (FIGS. 5B (pre-mixing), 5C (post-mixing, pre-phase separation),
and 5D (post-phase separation)), a second sample was prepared by
combining Thy:Men (1:1) DES and contaminated freshwater at a 1:1
v/v (FIGS. 6A (post-mixing, pre-phase separation), 6B (post-phase
separation)), a third sample was prepared by combining Dea:Men
(1:1) with contaminated freshwater at a 1:10 v/v (FIG. 7), and a
fourth sample was prepared by combining Dea:Men (1:1) with
contaminated salty water at a 1:10 v/v (FIG. 8). Each hydrophobic
DES initially formed a clear layer on top of the contaminated water
sample with which it was combined (as shown, e.g., in FIG. 5B).
Following the initial combination of hydrophobic DES and
contaminated water sample (as shown, e.g., in FIGS. 5C and 6A),
each mixture was allowed to either sit or was centrifuged at 1,000
rpm for two minutes for phase separation (as shown in FIGS. 5D, 6B,
7, and 8).
[0061] Water Repulsion and DES Affinity to PET
[0062] The water-repellent property of PET and the affinity between
PET and DESs were characterized by measuring the static contact
angle, which is determined between a liquid droplet and a surface.
Generally, a solid surface is considered as hydrophobic if its
contact angle against water is larger than 90.degree..
[0063] Free Energy of PET from Aqueous to DES Phase
[0064] The free energy profile for transferring a PET 5-monomer
chain from the water phase to a hydrophobic DES synthesized from
thymol and menthol at a molar ratio of 2:1 (Thy:Men (2:1) DES)
using well-tempered metadynamics simulations was also explored. The
simulation system was built by placing the PET chain in the water
phase. FIG. 10 shows a snapshot of the initial configuration for
the simulation system. The position of the center of mass of the
PET chain was used as the collective variable in the well-tempered
metadynamics. The whole simulation was conducted using Groningen
Machine for Chemical Simulations (GROMACS) and PLUMED-implemented
GROMACS.
[0065] Results and Discussion
[0066] Nanoplastic Extraction from Contaminated Water Samples
[0067] Nanoplastic extraction was observed in the DES phase (i.e.,
the portion of the mixture containing the hydrophobic DES and
floating above the aqueous portion of the mixture) of each sample
tested. As such, the nanoplastics observed within the DES phase of
the samples shown in FIGS. 5D, 6B, 7, and 8 thus evidence that both
Dea:Men (1:1) DES and Thy:Men (1:1) DES are hydrophobic DESs
capable of extracting nanoplastic particles from contaminated water
samples. It was observed that the plastic particles were evenly
distributed in the DES phase of the sample including Dea:Men (1:1)
mixed with contaminated freshwater at a 1:1 v/v (FIG. 5D), whereas
the nanoplastics extracted in the sample including Thy:Men (1:1)
mixed with contaminated freshwater at a 1:1 v/v tended to stay in
the water/DES interface (FIG. 6B). It was also observed that
greater nanoplastic extraction occurred in the sample including
Dea:Men (1:1) mixed with contaminated salty water at a 1:10 v/v
(FIG. 8) than the sample including Dea:Men (1:1) mixed with
contaminated freshwater at a 1:10 v/v (FIG. 7). The tendency of
nanoplastics to aggregate in clusters of larger particle size in
salty water as compared to freshwater (FIG. 4) appears to
facilitate greater plastic contaminant extraction and presence
within the hydrophobic DES phase.
[0068] Water Repulsion and DES Affinity to PET
[0069] FIG. 9 shows the contact angles of freshwater (indicated
with the label "Water") and the hydrophobic DES of Dea:Men (1:1)
(indicated with label "DES-A") and the hydrophobic DES of Thy:Men
(1:1) (indicated with label "DES-B") toward PET. When dropping 104,
of freshwater onto a flat PET film, the contact angle was around
95.52.+-.1.55.degree., which indicates a hydrophobic surface. But
when dropping the same amount of DES solvents onto the PET film,
the contact angle significantly declined to around
28.35.+-.1.34.degree. for Dea:Men (1:1) DES and to around
30.80.+-.1.56 for Thy:Men (1:1) DES, suggesting a strong affinity
between PET and the DES solvents of Dea:Men (1:1) DES and Thy:Men
(1:1) DES.
[0070] Free Energy of PET from Aqueous to DES Phase
[0071] The free energy profile confirms that the interface plays an
important role in the distribution of PET chains in the DES-water
sample systems. FIG. 11 shows the free energy profile as a function
of the position of the center of mass of PET chain around the
interface in the DES-water system. The fluctuation of the free
energy profile shows that distribution of the PET chains varies as
a function of their distance to the interface.
Example 2
[0072] Materials and Methods
[0073] The plastic contaminant extraction efficiency within a
freshwater sample contaminated by PET was measured for three
different hydrophobic DESs: (i) Dea:Men (1:1); (ii) Dea:Men (1:2);
and (iii) Thy:Men (1:1).
[0074] The contaminated water sample in which each hydrophobic DES
was implemented contained 1 mg/ml PET nanoplastics, a concentration
much higher than the concentration typically found in environmental
samples. Each contaminated water sample was prepared using PET
pellets in the same manner and using the same methods as described
above in Example 1.
[0075] The first hydrophobic DES was synthesized by mixing decanoic
acid and menthol at a 1:1 molar ratio, the second hydrophobic DES
was synthesized by mixing decanoic acid and menthol at a 1:2 molar
ratio, and the third hydrophobic DES was synthesized by mixing
thymol with menthol at a 1:1 molar ratio. Each eutectic mixture was
followed by heating to 60.degree. C. with a constant stirring until
a homogenous and transparent liquid was obtained.
[0076] A total of three samples were prepared for by mixing each of
the three hydrophobic DESs (Dea:Men (1:1); Dea:Men (1:2); and
Thy:Men (1:1)) with the contaminated water sample at a 1:1 v/v.
Following the initial combination of the hydrophobic DES and
contaminated water sample, each mixture was constantly stirred for
32 hours. Over the course of the 32-hour period, the percentage of
PET plastic contaminants extracted from each water sample was
measured by optical density reading at 600 nm in the aqueous
portion of the mixture.
[0077] Results and Discussion
[0078] The extraction efficiency of the hydrophobic DESs across the
three samples ranged from 87% to 91%. Specifically, it was found
that the sample with Dea:Men (1:1) plateaued at 90% of PET
extracted, the sample with Dea:Men (1:2) plateaued at 91% of PET
extracted, and Thy:Men (1:1) plateaued at 87% of PET extracted
(FIG. 12).
[0079] All publications, patents, and patent applications mentioned
in this specification are herein incorporated by reference to the
same extent as if each individual publication, patent, or patent
application was specifically and individually indicated to be
incorporated by reference, including the references set forth in
the following references list:
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[0122] It will be understood that various details of the presently
disclosed subject matter can be changed without departing from the
scope of the subject matter disclosed herein. Furthermore, the
foregoing description is for the purpose of illustration only, and
not for the purpose of limitation.
* * * * *